501 results on '"Škoda, P."'
Search Results
2. Brane mechanics and gapped Lie n-algebroids
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Chatzistavrakidis, Athanasios, Kodžoman, Toni, and Škoda, Zoran
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High Energy Physics - Theory ,Mathematical Physics ,Mathematics - Differential Geometry - Abstract
We draw a parallel between the BV/BRST formalism for higher-dimensional ($\ge 2$) Hamiltonian mechanics and higher notions of torsion and basic curvature tensors for generalized connections in specific Lie $n$-algebroids based on homotopy Poisson structures. The gauge systems we consider include Poisson sigma models in any dimension and ``generalised R-flux'' deformations thereof, such as models with an $(n+2)$-form-twisted R-Poisson target space. Their BV/BRST action includes interaction terms among the fields, ghosts and antifields whose coefficients acquire a geometric meaning by considering twisted Koszul multibrackets that endow the target space with a structure that we call a gapped almost Lie $n$-algebroid. Studying covariant derivatives along $n$-forms, we define suitable polytorsion and basic polycurvature tensors and identify them with the interaction coefficients in the gauge theory, thus relating models for topological $n$-branes to differential geometry on Lie $n$-algebroids., Comment: 37 pages
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- 2024
3. Ultrapotassic plutons as a source of uranium of vein-type U-deposits (Moldanubian Zone, Bohemian Massif): insights from SIMS uraninite U–Pb dating and trace element geochemistry
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Kubeš, Martin, Leichmann, Jaromír, Wertich, Vojtěch, Čopjaková, Renata, Holá, Markéta, Škoda, Radek, Kříbek, Bohdan, Mercadier, Julien, Cuney, Michel, Deloule, Etienne, Lecomte, Andreï, and Krzemińska, Ewa
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- 2024
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4. Knowledge Graphs for the Life Sciences: Recent Developments, Challenges and Opportunities
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Chen, Jiaoyan, Dong, Hang, Hastings, Janna, Jiménez-Ruiz, Ernesto, López, Vanessa, Monnin, Pierre, Pesquita, Catia, Škoda, Petr, and Tamma, Valentina
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Computer Science - Artificial Intelligence ,Computer Science - Computation and Language ,I.2.4 ,J.3 - Abstract
The term life sciences refers to the disciplines that study living organisms and life processes, and include chemistry, biology, medicine, and a range of other related disciplines. Research efforts in life sciences are heavily data-driven, as they produce and consume vast amounts of scientific data, much of which is intrinsically relational and graph-structured. The volume of data and the complexity of scientific concepts and relations referred to therein promote the application of advanced knowledge-driven technologies for managing and interpreting data, with the ultimate aim to advance scientific discovery. In this survey and position paper, we discuss recent developments and advances in the use of graph-based technologies in life sciences and set out a vision for how these technologies will impact these fields into the future. We focus on three broad topics: the construction and management of Knowledge Graphs (KGs), the use of KGs and associated technologies in the discovery of new knowledge, and the use of KGs in artificial intelligence applications to support explanations (explainable AI). We select a few exemplary use cases for each topic, discuss the challenges and open research questions within these topics, and conclude with a perspective and outlook that summarizes the overarching challenges and their potential solutions as a guide for future research., Comment: 33 pages, 1 figure, camera-ready version, accepted for Transactions on Graph Data and Knowledge (TGDK)
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- 2023
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5. Enveloping algebra is a Yetter--Drinfeld module algebra over Hopf algebra of regular functions on the automorphism group of a Lie algebra
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Škoda, Zoran and Stojić, Martina
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Mathematics - Quantum Algebra ,16T05, 16S40, 16T10 - Abstract
We present an elementary construction of a (highly degenerate) Hopf pairing between the universal enveloping algebra $U(\mathfrak{g})$ of a finite-dimensional Lie algebra $\mathfrak{g}$ over arbitrary field $\mathbf{k}$ and the Hopf algebra $\mathcal{O}(\mathrm{Aut}(\mathfrak{g}))$ of regular functions on the automorphism group of $\mathfrak{g}$. This pairing induces a Hopf action of $\mathcal{O}(\mathrm{Aut}(\mathfrak{g}))$ on $U(\mathfrak{g})$ which together with an explicitly given coaction makes $U(\mathfrak{g})$ into a braided commutative Yetter--Drinfeld $\mathcal{O}(\mathrm{Aut}(\mathfrak{g}))$-module algebra. From these data one constructs a Hopf algebroid structure on the smash product algebra $\mathcal{O}(\mathrm{Aut}(\mathfrak{g}))\sharp U(\mathfrak{g})$ retaining essential features from earlier constructions of a Hopf algebroid structure on infinite-dimensional versions of Heisenberg double of $U(\mathfrak{g})$, including a noncommutative phase space of Lie algebra type, while avoiding the need of completed tensor products. We prove a slightly more general result where algebra $\mathcal{O}(\mathrm{Aut}(\mathfrak{g}))$ is replaced by $\mathcal{O}(\mathrm{Aut}(\mathfrak{h}))$ and where $\mathfrak{h}$ is any finite-dimensional Leibniz algebra having $\mathfrak{g}$ as its maximal Lie algebra quotient., Comment: v2: 18 pages, title slightly changed, presentation thoroughly revised
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- 2023
6. Comment on 'Twisted bialgebroids versus bialgebroids from Drinfeld twist'
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Škoda, Zoran and Stojić, Martina
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Mathematics - Quantum Algebra ,16T10, 16S40, 16T05 - Abstract
A class of left bialgebroids whose underlying algebra $A\sharp H$ is a smash product of a bialgebra $H$ with a braided commutative Yetter--Drinfeld $H$-algebra $A$ has recently been studied in relation to models of field theories on noncommutative spaces. In [A. Borowiec, A. Pachol, ``Twisted bialgebroids versus bialgebroids from a Drinfeld twist'', J. Phys. A50 (2017) 055205] a proof has been presented that the bialgebroid $A_F\sharp H^F$ where $H^F$ and $A_F$ are the twists of $H$ and $A$ by a Drinfeld 2-cocycle $F = \sum F^1\otimes F^2$ is isomorphic to the twist of the bialgebroid $A\sharp H$ by the bialgebroid 2-cocycle $\sum 1\sharp F^1\otimes 1\sharp F^2$ induced by $F$. They assume $H$ is quasitriangular, which is reasonable for many physical applications. However the proof and the entire paper take for granted that the coaction and the prebraiding are both given by special formulas involving the R-matrix. There are counterexamples of Yetter--Drinfeld modules over quasitriangular Hopf algebras which are not of this special form. Nevertheless, the main result essentially survives. We present a proof with general coaction and the correct prebraiding, and even without the assumption of quasitriangularity., Comment: v2: 10 pages, improved presentation, in particular more structured exposition in Sec. 2 and 3. Added Concluding remarks (Sec. 4) and few references. To appear in J. Phys. A
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- 2023
7. Interactions between flow fields induced by surface dielectric barrier discharge arrays
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Böddecker, Alexander, Passmann, Maximilian, Wilczek, Sebastian, Schücke, Lars, Korolov, Ihor, Skoda, Romuald, Mussenbrock, Thomas, Gibson, Andrew R., and Awakowicz, Peter
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Physics - Plasma Physics - Abstract
This study investigates the flow field induced by a surface dielectric barrier discharge (SDBD) system, known for its efficient pollution remediation of volatile organic compounds (VOCs). We aim to understand the flow dynamics that contribute to the high conversion observed in similar systems. Experimental techniques, including schlieren imaging and particle image velocimetry (PIV), applied with high temporal resolution, were used to analyse the flow field. Complementary, fluid simulations are employed to investigate the coupling between streamer and gas dynamics. Results show distinct fluid field behaviours for different electrode configurations, which differ in geometric complexity. The fluid field analysis of the most basic electrode design revealed behaviours commonly observed in actuator studies. The simulation results indicate the local information about the electron density as well as different temporal phases of the fluid flow. The electrode design with mostly parallel grid line structures exhibits confined vortices near the surface. In contrast, an electrode design also used in previous studies, is shown to promote strong gas transport through extended vortex structures, enhancing gas mixing and potentially explaining the high conversion observed., Comment: submitted to Plasma Chemistry and Plasma Processing by Springer Nature
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- 2023
8. Brane mechanics and gapped Lie n-algebroids
- Author
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Athanasios Chatzistavrakidis, Toni Kodžoman, and Zoran Škoda
- Subjects
Differential and Algebraic Geometry ,BRST Quantization ,P-Branes ,Sigma Models ,Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Abstract We draw a parallel between the BV/BRST formalism for higher-dimensional (≥ 2) Hamiltonian mechanics and higher notions of torsion and basic curvature tensors for generalized connections in specific Lie n-algebroids based on homotopy Poisson structures. The gauge systems we consider include Poisson sigma models in any dimension and “generalised R-flux” deformations thereof, such as models with an (n + 2)-form-twisted R-Poisson target space. Their BV/BRST action includes interaction terms among the fields, ghosts and antifields whose coefficients acquire a geometric meaning by considering twisted Koszul multibrackets that endow the target space with a structure that we call a gapped almost Lie n-algebroid. Studying covariant derivatives along n-forms, we define suitable polytorsion and basic polycurvature tensors and identify them with the interaction coefficients in the gauge theory, thus relating models for topological n-branes to differential geometry on Lie n-algebroids.
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- 2024
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9. Exploring moral competence regression: a narrative approach in medical ethics education for medical students
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Zielina, Martin, Škoda, Jaromír, Ivanová, Kateřina, Dostál, Daniel, Juríčková, Lubica, Anthony Procházka, David, Straka, Barbora, and Doležal, Adam
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- 2024
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10. Acute and long-term results with the 3rd generation visually guided laser balloon ablation system for pv isolation
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Funasako, Moritoshi, Petrů, Jan, Hála, Pavel, Janotka, Marek, Škoda, Jan, Chovanec, Milan, Šedivá, Lucie, Reddy, Vivek Y., and Neužil, Petr
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- 2024
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11. Zvěstovite-(Fe), Ag6(Ag4Fe2)As4S13, a new member of the tetrahedrite group from the Ulatayskoe Ag–Cu–Co occurrence, eastern Siberia, Russia
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C. Biagioni, A. V. Kasatkin, F. Nestola, R. Škoda, V. V. Gurzhiy, A. A. Agakhanov, and N. N. Koshlyakova
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Mineralogy ,QE351-399.2 - Abstract
The new mineral zvěstovite-(Fe), ideally Ag6(Ag4Fe2)As4S13, has been found in the small abandoned Ulatayskoe Ag–Cu–Co occurrence, Ovyurskiy District, Tuva Republic, eastern Siberia, Russia. It occurs as anhedral grains, up to 1 × 0.4 mm in size but usually much smaller, closely intergrown with native silver, in Mg-bearing siderite–quartz gangue. Other associated minerals include acanthite, cobaltite, As-rich members of the tetrahedrite group (kenoargentotennantite-(Fe), tennantite-(Zn), zvěstovite-(Zn)), gersdorffite, jalpaite, krutovite, löllingite, pearceite, safflorite, skutterudite, Br-bearing chlorargyrite, malachite, and muscovite. Zvěstovite-(Fe) is iron black and opaque and has a black streak and metallic lustre. It is brittle and has a conchoidal fracture. No cleavage or parting is observed. The Vickers micro-indentation hardness (Vickers hardness number, VHN; 25 g load) is 169 kg mm−2 (range of 149–187 kg mm−2, n=4), corresponding to a Mohs hardness of 3–3.5. The calculated density is 4.979 g cm−3. In reflected light, zvěstovite-(Fe) is light grey with a greenish tint and isotropic. Internal reflections are ubiquitous and deep red in colour. The reflectance values for wavelengths recommended by the Commission on Ore Mineralogy of the International Mineralogical Association are (R, %): 32.5 (470 nm), 31.1 (546 nm), 30.1 (589 nm), and 28.8 (650 nm). The chemical composition (wt %, electron microprobe data, mean of eight spot analyses) is as follows: Cu 1.81, Ag 56.02, Fe 4.60, Zn 0.01, As 13.85, Sb 2.63, S 21.50, total 100.42. The empirical formula, calculated on the basis of 16 atoms per formula unit, is Ag9.93Cu0.54Fe1.58As3.54Sb0.41S12.83. Zvěstovite-(Fe) is cubic and has a space group of I4‾3m, with a=10.8601(3), V=1280.86(11) Å3, and Z=2. The strongest lines of the X-ray powder diffraction pattern (d, Å (I, %) hkl) are 7.68 (11) 110, 3.136 (100) 222, 2.717 (12) 400, 1.984 (8) 521, 1.921 (23) 440, and 1.638 (11) 622. The crystal structure of zvěstovite-(Fe) was refined to R1=0.0551 for 400 unique reflections with Fo>4σ (Fo). The possible ordering of the split M(2) sites is discussed. The new mineral is the Fe isotype of zvěstovite-(Zn). Both these minerals form the zvěstovite series within the tetrahedrite group.
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- 2024
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12. Exploring moral competence regression: a narrative approach in medical ethics education for medical students
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Martin Zielina, Jaromír Škoda, Kateřina Ivanová, Daniel Dostál, Lubica Juríčková, David Anthony Procházka, Barbora Straka, and Adam Doležal
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Moral competence ,Medical students ,Narrative approach ,Konstanz Method of Dilemma Discussion ,Problem-based learnig ,Case-based learning ,Medical philosophy. Medical ethics ,R723-726 - Abstract
Abstract Background Studies from different countries report a stagnation or regression of moral competence in medical students between the first and the last year of their studies, and the value of various educational interventions remains uncertain. Methods We used Moral Competence Test (MCT) to measure C-scores of moral competence to determine the change in the MCT C-scores between the first- and the fifth-year medical students from two medical schools in the Czech Republic in the academic year 2022/2023 and to analyze factors associated with the C-scores (observational study). In addition, for the first-year students, we compared the results of the MCT before and after an intervention in medical ethics curriculum (interventional study). We used a cross-sectional and descriptive design for the observational study. Students completed the MCT, consisting of two moral dilemmas (Worker´s Dilemma and Doctor´s Dilemma), the results measured by the C-score, which represents moral competence. Results In total, 685 students participated in the observational study. Objective 1: based on the analysis of the C-score, we observed a decrease in moral competence between the first and the fifth-year medical students (p
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- 2024
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13. Weighted Average-convexity and Cooperative Games
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Skoda, Alexandre and Venel, Xavier
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Computer Science - Computer Science and Game Theory ,Computer Science - Discrete Mathematics - Abstract
We generalize the notion of convexity and average-convexity to the notion of weighted average-convexity. We show several results on the relation between weighted average-convexity and cooperative games. First, we prove that if a game is weighted average-convex, then the corresponding weighted Shapley value is in the core. Second, we exhibit necessary conditions for a communication TU-game to preserve the weighted average-convexity. Finally, we provide a complete characterization when the underlying graph is a priority decreasing tree.
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- 2022
14. Semantic Web: Past, Present, and Future
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Scherp, Ansgar, Groener, Gerd, Škoda, Petr, Hose, Katja, and Vidal, Maria-Esther
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linked open data ,semantic web graphs ,knowledge graphs ,Electronic computers. Computer science ,QA75.5-76.95 - Abstract
Ever since the vision was formulated, the Semantic Web has inspired many generations of innovations. Semantic technologies have been used to share vast amounts of information on the Web, enhance them with semantics to give them meaning, and enable inference and reasoning on them. Throughout the years, semantic technologies, and in particular knowledge graphs, have been used in search engines, data integration, enterprise settings, and machine learning. In this paper, we recap the classical concepts and foundations of the Semantic Web as well as modern and recent concepts and applications, building upon these foundations. The classical topics we cover include knowledge representation, creating and validating knowledge on the Web, reasoning and linking, and distributed querying. We enhance this classical view of the so-called "Semantic Web Layer Cake" with an update of recent concepts that include provenance, security and trust, as well as a discussion of practical impacts from industry-led contributions. We conclude with an outlook on the future directions of the Semantic Web. This is a living document. If you like to contribute, please contact the first author and visit: https://github.com/ascherp/semantic-web-primer
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- 2024
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15. Symmetric ordering and Weyl realizations for quantum Minkowski spaces
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Meljanac, Stjepan, Škoda, Zoran, and Kresic-Juric, Sasa
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Mathematical Physics - Abstract
Symmetric ordering and Weyl realizations for non commutative quantum Minkowski spaces are reviewed. Weyl realizations of Lie deformed spaces and corresponding star products, as well as twist corresponding to Weyl realization and coproduct of momenta are presented. Drinfeld twists understood in Hopf algebroid sense are also discussed. A few examples of corresponding Weyl realizations are given. We show that for the original Snyder space there exists symmetric ordering, but no Weyl realization. Quadratic deformations of Minkowski space are considered and it is demonstrated that symmetric ordering is deformed and a generalized Weyl realization can be defined., Comment: 25 pages, to appear in J. Math. Physics
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- 2022
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16. Estimating flow fields with Reduced Order Models
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Sommer, Kamil David, Reineking, Lucas, Ravichandran, Yogesh Parry, Skoda, Romuald, and Mönnigmann, Martin
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Physics - Fluid Dynamics ,Electrical Engineering and Systems Science - Systems and Control - Abstract
The estimation of fluid flows inside a centrifugal pump in realtime is a challenging task that cannot be achieved with long-established methods like CFD due to their computational demands. We use a projection-based reduced order model (ROM) instead. Based on this ROM, a realtime observer can be devised that estimates the temporally and spatially resolved velocity and pressure fields inside the pump. The entire fluid-solid domain is treated as a fluid in order to be able to consider moving rigid bodies in the reduction method. A greedy algorithm is introduced for finding suitable and as few measurement locations as possible. Robust observability is ensured with an extended Kalman filter, which is based on a time-variant observability matrix obtained from the nonlinear velocity ROM. We present the results of the velocity and pressure ROMs based on a unsteady Reynolds-averaged Navier-Stokes CFD simulation of a 2D centrifugal pump, as well as the results for the extended Kalman filter., Comment: 20 pages, 12 figures
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- 2022
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17. A Survey of Novae in M83
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Shafter, A. W., Hornoch, K., Benáček, J., Galád, A., Janík, J., Juryšek, J., Kotková, L., Kurfürst, P., Kučáková, H., Kušnirák, P., Liška, J., Paunzen, E., Skarka, M., Škoda, P., Wolf, M., Zasche, P., and Zejda, M.
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Astrophysics - Astrophysics of Galaxies - Abstract
The results of the first synoptic survey of novae in the barred spiral and starburst galaxy, M83 (NGC 5236), are presented. A total of 19 novae and one background supernova were discovered during the course of a nearly seven-year survey comprised of over 200 individual nights of observation between 2012 December 12 and 2019 March 14. After correcting for the limiting magnitude and the spatial and temporal coverage of the survey, the nova rate in M83 was found to be $R=19^{+5}_{-3}$ yr$^{-1}$. This rate, when normalized to the $K$-band luminosity of the galaxy, yields a luminosity-specific nova rate, $\nu_K = 3.0^{+0.9}_{-0.6}\times10^{-10}$ yr$^{-1} L_{\odot,K}^{-1}$. The spatial distribution of the novae is found to be more extended than the overall galaxy light suggesting that the observed novae are likely dominated by a disk population. This result is consistent with the observed nova light curves which reveal that the M83 novae are on average more luminous at maximum light and fade faster when compared with novae observed in M31. Generally, the more luminous M83 novae were observed to fade more rapidly, with the complete sample being broadly consistent with a linear Maximum-Magnitude vs Rate of Decline relation., Comment: 24 pages, 12 figures, accepted for publication in the Astrophysical Journal
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- 2021
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18. Why blockchain and smart contracts need semantic descriptions
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Škoda, Zoran
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Computer Science - Computers and Society ,Computer Science - Distributed, Parallel, and Cluster Computing - Abstract
We argue that there is a hierarchy of levels describing to that particular level relevant features of reality behind the content and behavior of blockchain and smart contracts in their realistic deployment. Choice, design, audit and legal control of these systems could be more informed, easier and raised to a higher level, if research on foundations of these descriptions develops and sets the formalisms, tools and standards for such descriptions., Comment: early draft, to be significantly expanded
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- 2021
19. Generalized Heisenberg algebra, realizations of the $\mathfrak{gl}(n)$ algebra and applications
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Meljanac, Stjepan, Škoda, Zoran, and Štrajn, Rina
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Mathematical Physics - Abstract
We introduce the generalized Heisenberg algebra appropriate for realizations of the $\mathfrak{gl}(n)$ algebra. Linear realizations of the $\mathfrak{gl}(n)$ algebra are presented and the corresponding star product, coproduct of momenta and twist are constructed. The dual realization and dual $\mathfrak{gl}(n)$ algebra are considered. Finally, we present a general realization of the $\mathfrak{gl}(n)$ algebra, the corresponding coproduct of momenta and two classes of twists. These results can be applied to physical theories on noncommutative spaces of the $\mathfrak{gl}(n)$ type.
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- 2021
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20. European Real Estate Properties Valuation: Ten Years After Adopting IFRS 13
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Miroslav Škoda, Kateřina Bočková, and Viera Guzoňová
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accounting ,ifrs 13 ,u.s. gaap ,real estate ,quality ,disclosure ,statistical analysis. ,Technological innovations. Automation ,HD45-45.2 - Abstract
IFRS 13 had its mandatory implementation on January 1st, 2013. The new accounting standard, which represents one step closer to harmonization between U.S. GAAP and IFRS, aims to eliminate inconsistencies in fair value measurement and its related disclosures through the introduction of new reporting requirements, specifically for assets and liabilities with no active markets. Although these demands also encompass information concerning financial instruments, our focus was on the disclosure changes related to the fair value of investment properties, previously regulated solely by IAS 40. As investment properties comprise the majority of assets in the real estate industry, this sector was further examined. Through a statistical analysis of the sample companies’ annual reports for the periods immediately before and after the implementation of IFRS 13, the purpose of our descriptor-explanatory study was to investigate the level of compliance with IFRS 13 fair value disclosure requirements for investment properties in real estate companies in Europe. In order to answer this question, we first scrutinized the level of compliance with the new disclosure requirements brought up by the standard and then, intermediated by an adaptation of the model developed by Beretta & Bozzolan (2008), measured the disclosure quality for both periods considered. After data collection and analysis, our findings reveal that IFRS 13 does affect the disclosure quality of investment properties in real estate companies in Europe. Overall compliance is very high, while disclosure quality has increased since the implementation of IFRS 13. As a way to further broaden the research related to the more extensive disclosure requirements under IFRS 13, we suggest additional studies be undertaken where the point of view of the real estate companies could be explored. Moreover, it would be interesting to investigate whether the increased number of disclosures, both in relation to quantity and quality, is relevant from an analyst’s standpoint. Doi: 10.28991/HIJ-2023-04-03-04 Full Text: PDF
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- 2023
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21. Batoniite, [Al8(OH)14(H2O)18](SO4)5 ⋅ 5H2O, a new mineral with the [Al8(OH)14(H2O)18]10+ polyoxocation from the Cetine di Cotorniano Mine, Tuscany, Italy
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D. Mauro, C. Biagioni, J. Sejkora, Z. Dolníček, and R. Škoda
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Mineralogy ,QE351-399.2 - Abstract
The new mineral batoniite, [Al8(OH)14(H2O)18](SO4)5 ⋅ 5H2O, was discovered in the Cetine di Cotorniano Mine, Chiusdino, Siena, Tuscany, Italy. It occurs as hemispherical aggregates composed of brittle tabular crystals, up to 1 mm in size, white to colorless in color, with a white streak and a vitreous to greasy luster. Batoniite is biaxial negative, with α= 1.4833(6), β= 1.4948(6), γ= 1.5019(5) (589 nm), and 2V(meas.)= 71(1)∘. Electron microprobe analysis, affected by the dehydration of batoniite under the chamber vacuum, gave (in wt %) the following: Al2O3 33.48, Fe2O3 0.05, SO3 33.00, and H2Ocalc 44.41, total 110.94. It corresponds to the chemical formula (Al7.98Fe0.013+)Σ7.99(SO4)5.01(OH)13.95(H2O)18 ⋅ 5H2O. Batoniite is triclinic, belonging to space group P1‾, with a= 9.1757(6), b= 12.0886(9), c= 20.9218(15) Å, α= 82.901(3), β= 87.334(3), γ= 86.999(2)∘, V= 2297.8(3) Å3, and Z= 2. The crystal structure was refined to R1= 0.0916 for 8118 unique reflections with Fo>4σ(Fo) and 811 refined parameters and 60 restraints. Batoniite is characterized by isolated [Al8(OH)14(H2O)18]10+ polyoxocations, H-bonded to five interstitial (SO4)2− and five H2O groups. In type material, it is associated with gypsum and a poorly crystallized Al–Fe sulfate. The crystallization of batoniite is probably due to the action of H2SO4 on Al-bearing rocks of Paleozoic age cropping out in the Garibaldi Tunnel, the lowest mining level of the Cetine di Cotorniano Mine.
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- 2023
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22. Crystal chemistry of ferriallanite-(Ce) from Nya Bastnäs, Sweden: Chemical and spectroscopic study
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Sobek, Kamil, Losos, Zdeněk, Škoda, Radek, Holá, Markéta, and Nasdala, Lutz
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- 2023
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23. Natural and artificial OH defect incorporation into fluoride minerals at elevated temperature—a case study of sellaite, villiaumite and fluorite
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Talla, Dominik, Beran, Anton, and Škoda, Radek
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- 2023
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24. Fixed neutron absorbers for improved nuclear safety and better economics in nuclear fuel storage, transport and disposal
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M. Lovecký, J. Závorka, J. Jiřičková, Z. Ondráček, and R. Škoda
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Criticality safety ,Spent fuel ,Neutron absorber ,GBC-32 ,VVER ,Nuclear engineering. Atomic power ,TK9001-9401 - Abstract
Current designs of both large reactor units and small modular reactors utilize a nuclear fuel with increasing enrichment. This increasing demand for better nuclear fuel utilization is a challenge for nuclear fuel handling facilities. The operation with higher enriched fuels leads to reduced reserves to legislative and safety criticality limits of spent fuel transport, storage and final disposal facilities. Design changes in these facilities are restricted due to a boron content in steel and aluminum alloys that are limited by rolling, extrusion, welding and other manufacturing processes. One possible solution for spent fuel pools and casks is the burnup credit method that allows decreasing very high safety margins associated with the fresh fuel assumption in spent fuel facilities. This solution can be supplemented or replaced by an alternative solution based on placing the neutron absorber material directly into the fuel assembly, where its efficiency is higher than between fuel assemblies. A neutron absorber permanently fixed in guide tubes decreases system reactivity more efficiently than absorber sheets between the fuel assemblies. The paper summarizes possibilities of fixed neutron absorbers for various nuclear fuel and fuel handling facilities. Moreover, an absorber material was optimized to propose alternative options to boron. Multiple effective absorbers that do not require steel or aluminum alloy compatibility are discussed because fixed absorbers are placed inside zirconium or steel cladding.
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- 2023
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25. Active deep learning method for the discovery of objects of interest in large spectroscopic surveys
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Škoda, Petr, Podsztavek, Ondřej, and Tvrdík, Pavel
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Astrophysics - Instrumentation and Methods for Astrophysics ,Computer Science - Machine Learning - Abstract
Current archives of the LAMOST telescope contain millions of pipeline-processed spectra that have probably never been seen by human eyes. Most of the rare objects with interesting physical properties, however, can only be identified by visual analysis of their characteristic spectral features. A proper combination of interactive visualisation with modern machine learning techniques opens new ways to discover such objects. We apply active learning classification supported by deep convolutional networks to automatically identify complex emission-line shapes in multi-million spectra archives. We used the pool-based uncertainty sampling active learning driven by a custom-designed deep convolutional neural network with 12 layers inspired by VGGNet, AlexNet, and ZFNet, but adapted for one-dimensional feature vectors. The unlabelled pool set is represented by 4.1 million spectra from the LAMOST DR2 survey. The initial training of the network was performed on a labelled set of about 13000 spectra obtained in the region around H$\alpha$ by the 2m Perek telescope of the Ond\v{r}ejov observatory, which mostly contains spectra of Be and related early-type stars. The differences between the Ond\v{r}ejov intermediate-resolution and the LAMOST low-resolution spectrographs were compensated for by Gaussian blurring. After several iterations, the network was able to successfully identify emission-line stars with an error smaller than 6.5%. Using the technology of the Virtual Observatory to visualise the results, we discovered 1013 spectra of 948 new candidates of emission-line objects in addition to 664 spectra of 549 objects that are listed in SIMBAD and 2644 spectra of 2291 objects identified in an earlier paper of a Chinese group led by Wen Hou. The most interesting objects with unusual spectral properties are discussed in detail., Comment: To appear in Astronomy & Astrophysics Section 14- Catalogs and Data, 15 pages, 13 figures
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- 2020
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26. Inheritance of Convexity for the $\tilde{\mathcal{P}}_{\min}$-Restricted Game
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Skoda, Alexandre
- Subjects
Computer Science - Discrete Mathematics ,Mathematics - Combinatorics - Abstract
We consider a restricted game on weighted graphs associated with minimum partitions. We replace in the classical definition of Myerson restricted game the connected components of any subgraph by the sub-components obtained with a specific partition $\tilde{\mathcal{P}}_{\min}$. This partition relies on the same principle as the partition $\mathcal{P}_{\min}$ introduced by Grabisch and Skoda (2012) but restricted to connected coalitions. More precisely, this new partition $\tilde{\mathcal{P}}_{\min}$ is induced by the deletion of the minimum weight edges in each connected component associated with a coalition. We provide a characterization of the graphs satisfying inheritance of convexity from the underlying game to the restricted game associated with $\tilde{\mathcal{P}}_{\min}$.
- Published
- 2020
27. A Dolbeault lemma for temperate currents
- Author
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Skoda, Henri
- Subjects
Mathematics - Complex Variables - Abstract
We consider a bounded open Stein subset $\Omega$ of a complex Stein manifold $X$ of dimension $n$. We prove that if $f$ is a current on $X$ of bidegree $(p,q+1)$, $\bar\partial$-closed on $\Omega$, we can find a current $u$ on $X$ of bidegree $(p,q)$ which is a solution of the equation $\bar\partial u=f$ in $\Omega$. In other words, we prove that the Dolbeault complex of temperate currents on $\Omega$ (i.e. currents on $\Omega$ which extend to currents on $X$) is concentrated in degree $0$. Moreover if $f$ is a current on $X= C^n$ of order $k$, then we can find a solution $u$ which is a current on $C^n$ of order $k+2n+1$.
- Published
- 2020
28. On interpolations between Jordanian twists
- Author
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Meljanac, Daniel, Meljanac, Stjepan, Škoda, Zoran, and Štrajn, Rina
- Subjects
Mathematical Physics ,53D55, 16T05 - Abstract
We consider two families of Drinfeld twists generated from a simple Jordanian twist further twisted with 1-cochains. Using combinatorial identities, they are presented as a series expansion in the dilatation and momentum generators. These twists interpolate between two simple Jordanian twists. For an expansion of a family of twists $\mathcal{F}_{L,u}$, we also show directly that the 2-cocycle condition reduces to previously proven identities., Comment: 11 pages, continuation of our earlier work arXiv:1904.03993, SIGMA 15 (2019) 082
- Published
- 2020
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29. Excluded minors for the Klein Bottle II. Cascades
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Mohar, Bojan and Škoda, Petr
- Subjects
Mathematics - Combinatorics - Abstract
Graphs that are critical (minimal excluded minors) for embeddability in surfaces are studied. In Part I, it was shown that graphs that are critical for embeddings into surfaces of Euler genus $k$ or for embeddings into nonorientable surface of genus $k$ are built from 3-connected components, called hoppers and cascades. In Part II, all cascades for Euler genus 2 are classified. As a consequence, the complete list of obstructions of connectivity 2 for embedding graphs into the Klein bottle is obtained., Comment: The original paper arxiv:1406.1341 was split into two parts, this is Part II
- Published
- 2020
30. Excluded minors for the Klein Bottle I. Low connectivity case
- Author
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Mohar, Bojan and Škoda, Petr
- Subjects
Mathematics - Combinatorics ,05C10 - Abstract
Graphs that are critical (minimal excluded minors) for embeddability in surfaces are studied. In Part I we consider the structure of graphs with a 2-vertex-cut that are critical with respect to the Euler genus. A general theorem describing the building blocks is presented. These constituents, called hoppers and cascades, are classified for the case when Euler genus is small. As a consequence, the complete list of obstructions of connectivity 2 for embedding graphs into the Klein bottle is obtained. This is the first complete result about obstructions for embeddability of graphs in the Klein bottle, and the outcome is somewhat surprising in the sense that there are considerably fewer excluded minors than expected., Comment: The full paper that was originally arXiv:1406.1341 has been split into two parts. This is Part I
- Published
- 2020
31. A note on symmetric orderings
- Author
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Škoda, Zoran
- Subjects
Mathematics - Quantum Algebra ,Mathematics - Rings and Algebras ,16S30, 16S32 - Abstract
Let $\hat{A}_n$ be the completion by the degree of a differential operator of the $n$-th Weyl algebra with generators $x_1,\ldots,x_n,\partial^1,\ldots,\partial^n$. Consider $n$ elements $X_1,\ldots,X_n$ in $\hat{A}_n$ of the form $$ X_i = x_i + \sum_{K = 1}^\infty \sum_{l = 1}^n\sum_{j = 1}^n x_l p_{ij}^{K-1,l}(\partial)\partial^j, $$ where $p^{K-1,l}_{ij}(\partial)$ is a degree $(K-1)$ homogeneous polynomial in $\partial^1,\ldots,\partial^n$, antisymmetric in subscripts $i,j$. Then for any natural $k$ and any function $i : \{1,\ldots,k\}\to\{1,\ldots,n\}$ we prove $$ \sum_{\sigma \in \Sigma(k)} X_{i_{\sigma(1)}}\cdots X_{i_{\sigma(k)}}\triangleright 1 = k! \,x_{i_1}\cdots x_{i_k}, $$ where $\Sigma(k)$ is the symmetric group on $k$ letters and $\triangleright$ denotes the Fock action of the $\hat{A}_n$ on the space of (commutative) polynomials., Comment: 8 pages, v2: expositional improvements and corrections; the second half of the main theorem's proof written much more explicitly
- Published
- 2020
32. Ondr}ejov echelle spectrograph, ground based support facility for exoplanet missions
- Author
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Kabath, Petr, Skarka, Marek, Sabotta, Silvia, Guenther, Eike, Jones, David, Klocova, Tereza, Subjak, Jan, Zak, Jiri, Spokova, Magdalena, Blazek, Martin, Dvorakova, Jana, Dupkala, Daniel, Fuchs, Jan, Hatzes, Artie, Kortusova, Eva, Novotny, Radek, Plavalova, Eva, Rezba, Ludek, Sloup, Jan, Skoda, Petr, and Slechta, Miroslav
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
Fulfilling the goals of space-based exoplanetary transit surveys, like Kepler and TESS, is impossible without ground-based spectroscopic follow-up. In particular, the first-step vetting of candidates could easily necessitate several hundreds of hours of telescope time -- an area where 2-m class telescopes can play a crucial role. Here, we describe the results from the science verification of the Ond\v{r}ejov Echelle Spectrograph (OES) installed on the 2-m Perek telescope. We discuss the performance of the instrument as well as its suitability for the study of exoplanetary candidates from space-based transit surveys. In spite of being located at an average European observing site, and originally being conceived for the study of variable stars, OES can prove to be an important instrument for the exoplanetary community in the TESS and PLATO era -- reaching accuracies of a few tens of m/s with reasonable sampling and signal-to-noise for sources down to V$\sim$13. The stability of OES is demonstrated via long-term monitoring of the standard star HD~109358, while its validity for exoplanetary candidate verification is shown using three K2 candidates EPIC~210925707, EPIC~206135267 and EPIC~211993818, to reveal that they are false positive detections., Comment: accepted for publication in PASP
- Published
- 2020
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33. Interpolations between Jordanian twists, the Poincar\'e-Weyl algebra and dispersion relations
- Author
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Meljanac, Daniel, Meljanac, Stjepan, Škoda, Zoran, and Štrajn, Rina
- Subjects
High Energy Physics - Theory ,Mathematical Physics - Abstract
We consider a two parameter family of Drinfeld twists generated from a simple Jordanian twist further twisted by 1-cochains. Twists from this family interpolate between two simple Jordanian twists. Relations between them are constructed and discussed. It is proved that there exists a one parameter family of twists identical to a simple Jordanian twist. The twisted coalgebra, star product and coordinate realizations of the $\kappa$-Minkowski noncommutative space time are presented. Real forms of Jordanian deformations are also discussed. The method of similarity transformations is applied to the Poincar\'e-Weyl Hopf algebra and two types of one parameter families of dispersion relations are constructed. Mathematically equivalent deformations, that are related to nonlinear changes of symmetry generators and linked with similarity maps, may lead to differences in the description of physical phenomena., Comment: to be published in Int. J. Mod. Phys. A
- Published
- 2019
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- View/download PDF
34. Decision-tree and ensemble-based mortality risk models for hospitalized patients with COVID-19
- Author
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Yaroslav Vyklyuk, Svitlana Levytska, Denys Nevinskyi, Kateryna Hazdiuk, Miroslav Škoda, Stanislav Andrushko, and Maryna Palii
- Subjects
covid-19 ,decision-making system ,decision tree ,ml-ensemble ,ensemble of classification models ,Electronic computers. Computer science ,QA75.5-76.95 - Abstract
The work is devoted to studying SARS-CoV-2-associated pneumonia and the investigating of the main indicators that lead to the patients’ mortality. Using the good-known parameters that are routinely embraced in clinical practice, we obtained new functional dependencies based on an accessible and understandable decision tree and ML ensemble of classifiers models that would allow the physician to determine the prognosis in a few minutes and, accordingly, to understand the need for treatment adjustment, transfer of the patient to the emergency department. The accuracy of the resulting ensemble of models fitted on actual hospital patient data was in the range of 0.88–0.91 for different metrics. Creating a data collection system with further training of classifiers will dynamically increase the forecast’s accuracy and automate the doctor’s decision-making process.
- Published
- 2023
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35. Multi-stage alteration history of volcanic clasts containing buddigtonite from Upper Cretaceous strata of the Subsilesian Unit, Czech part of the Outer Flysch Carpathians
- Author
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Matýsek, Dalibor, Skupien, Petr, Bubík, Miroslav, Jirásek, Jakub, and Škoda, Radek
- Published
- 2022
- Full Text
- View/download PDF
36. Open dataset discovery using context-enhanced similarity search
- Author
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Bernhauer, David, Nečaský, Martin, Škoda, Petr, Klímek, Jakub, and Skopal, Tomáš
- Published
- 2022
- Full Text
- View/download PDF
37. Properties and nature of Be stars 31. The binary nature, light variability, physical elements, and emission-line changes of HD~81357
- Author
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Koubský, P., Harmanec, P., Brož, M., Kotková, L., Yang, S., Božić, H., Sudar, D., Frémat, Y., Korčákov'a, D., Votruba, V., Škoda, P., Šlechta, M., and Ruždjak, D.
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
Reliable determination of the basic physical properties of hot emission-line binaries with Roche-lobe filling secondaries is important for developing the theory of mass exchange in binaries. It is not easy, however, due to the presence of circumstellar matter. Here, we report the first detailed investigation of a new representative of this class of binaries, HD~81357, based on the analysis of spectra and photometry from several observatories. HD~81357 was found to be a double-lined spectroscopic binary and an ellipsoidal variable seen under an intermediate orbital inclination of $\sim(63\pm5)^\circ$, having an orbital period of 33\fd77445(41) and a~circular orbit. From an automated comparison of the observed and synthetic spectra, we estimate the component's effective temperatures to be 12930(540)~K and 4260(24)~K. The combined light-curve and orbital solutions, also constrained by a very accurate Gaia Data Release 2 parallax, give the following values of the basic physical properties: masses $3.36\pm0.15$ and $0.34\pm0.04$~\Mnom, radii $3.9\pm0.2$ and 13.97\pm0.05$~\Rnom, and a~mass ratio $10.0\pm0.5$. Evolutionary modelling of the system including the phase of mass transfer between the components indicated that HD~81357 is a~system observed in the final slow phase of the mass exchange after the mass-ratio reversal. Contrary to what has been seen for similar binaries like AU~Mon, no cyclic light variations were found on a~time scale an~order of magnitude longer than the orbital period. 243,1 15%, Comment: 16 pages, 9 figures; accepted for publication in Astronomy and Astrophysics
- Published
- 2019
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38. One Parameter Family of Jordanian Twists
- Author
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Meljanac, Daniel, Meljanac, Stjepan, Škoda, Zoran, and Štrajn, Rina
- Subjects
Mathematical Physics ,Mathematics - Quantum Algebra - Abstract
We propose an explicit generalization of the Jordanian twist proposed in $r$-symmetrized form by Giaquinto and Zhang. It is proved that this generalization satisfies the 2-cocycle condition. We present explicit formulas for the corresponding star product and twisted coproduct. Finally, we show that our generalization coincides with the twist obtained from the simple Jordanian twist by twisting by a 1-cochain.
- Published
- 2019
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- View/download PDF
39. Direct detection of beer photodegradation in commercial bottles and introduction of a new Light-Struck Flavour Susceptibility Index
- Author
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Petr Gabriel, Jakub Škoda, Karolína Benešová, and Dagmar Matoulková
- Subjects
beer ,light-struck flavour ,photodegradation ,3-methyl-2-butene-1-thiol ,riboflavin ,Fermentation industries. Beverages. Alcohol ,TP500-660 - Abstract
Exposure of beer to light results in the formation of undesirable flavours or complete spoilage. Photo-damaged beer has a specific, so-called skunky or light-struck flavour (LSF). The compound responsible for LSF is 3-methylbut-2- ene-1-thiol (MBT). Riboflavin (RF) plays a key role in the formation of MBT. It absorbs light in the blue part of the spectrum and transfers excitation energy to isohumulones. This process is accompanied by the decomposition of RF, which causes a decrease in the absorbance of the sample at 450 nm. The decomposition is directly related to the formation of LSF. In this study, the decrease in absorbance associated with the defined illumination of model and real beer directly in commercial bottles was measured. The decrease in absorbance correlated with the decrease in RF concentration and the formation of LSF detected by the sensory panel. The Light-Struck Flavour Susceptibility Index was introduced as a rate of the beer susceptibility to light degradation and the formation of LSF.
- Published
- 2022
- Full Text
- View/download PDF
40. A Managerial Approach towards Modeling the Different Strains of the COVID-19 Virus Based on the Spatial GeoCity Model
- Author
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Yaroslav Vyklyuk, Denys Nevinskyi, Valentyna Chopyak, Miroslav Škoda, Olga Golubovska, and Kateryna Hazdiuk
- Subjects
multi-agent system ,GEO-spatial simulation model ,COVID-19 ,modelling ,geo-object ,real-time simulation ,Microbiology ,QR1-502 - Abstract
This study proposes a modification of the GeoCity model previously developed by the authors, detailing the age structure of the population, personal schedule on weekdays and working days, and individual health characteristics of the agents. This made it possible to build a more realistic model of the functioning of the city and its residents. The developed model made it possible to simulate the spread of three types of strain of the COVID-19 virus, and to analyze the adequacy of this model in the case of unhindered spread of the virus among city residents. Calculations based on the proposed model show that SARS-CoV 2 spreads mainly from contacts in workplaces and transport, and schoolchildren and preschool children are the recipients, not the initiators of the epidemic. The simulations showed that fluctuations in the dynamics of various indicators of the spread of SARS-CoV 2 were associated with the difference in the daily schedule on weekdays and weekends. The results of the calculations showed that the daily schedules of people strongly influence the spread of SARS-CoV 2. Under assumptions of the model, the results show that for the more contagious “rapid” strains of SARS-CoV 2 (omicron), immunocompetent people become a significant source of infection. For the less contagious “slow strains” (alpha) of SARS-CoV 2, the most active source of infection is immunocompromised individuals (pregnant women). The more contagious, or “fast” strain of the SARS-CoV 2 virus (omicron), spreads faster in public transport. For less contagious, or “slow” strains of the virus (alpha), the greatest infection occurs due to work and educational contacts.
- Published
- 2023
- Full Text
- View/download PDF
41. Fuzzy and robust approach for decision-making in disaster situations
- Author
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Nehézová, Tereza Sedlářová, Škoda, Michal, Hlavatý, Robert, and Brožová, Helena
- Published
- 2022
- Full Text
- View/download PDF
42. Multivalent Ion-Activated Protein Adsorption Reflecting Bulk Reentrant Behavior
- Author
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Fries, Madeleine R., Stopper, Daniel, Braun, Michal K., Hinderhofer, Alexander, Zhang, Fajun, Jacobs, Robert M. J., Skoda, Maximilian W. A., Hansen-Goos, Hendrik, Roth, Roland, and Schreiber, Frank
- Subjects
Physics - Biological Physics ,Condensed Matter - Soft Condensed Matter - Abstract
Protein adsorption at the solid-liquid interface is an important phenomenon that often can be observed as a first step in biological processes. Despite its inherent importance, still relatively little is known about the underlying microscopic mechanisms. Here, using multivalent ions, we demonstrate the control of the interactions and the corresponding adsorption of net-negatively charged proteins (bovine serum albumin) at a solid-liquid interface. This is demonstrated by ellipsometry and corroborated by neutron reflectivity and quartz-crystal microbalance experiments. We show that the reentrant condensation observed within the rich bulk phase behavior of the system featuring a nonmonotonic dependence of the second virial cofficient on salt concentration c_s is reflected in an intriguing way in the protein adsorption d(c_s) at the interface. Our findings are successfully described and understood by a model of ion-activated patchy interactions within the framework of classical density functional theory. In addition to the general challenge of connecting bulk and interface behavior, our work has implications for, inter alia, nucleation at interfaces., Comment: 5 pages, 3 Figures, accepted by Phys. Rev. Lett
- Published
- 2017
- Full Text
- View/download PDF
43. Redefinition of beraunite, Fe3+6(PO4)4O(OH)4 ⋅ 6H2O, and discreditation of the name eleonorite: a re-investigation of type material from the Hrbek Mine (Czech Republic)
- Author
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L. Vrtiška, J. Tvrdý, J. Plášil, J. Sejkora, R. Škoda, N. V. Chukanov, A. Massanek, J. Filip, Z. Dolníček, and F. Veselovský
- Subjects
Mineralogy ,QE351-399.2 - Abstract
Re-investigation of the type material of beraunite from the Hrbek Mine, Svatá Dobrotivá, Czech Republic, proved the identity of beraunite and eleonorite. Based on this study, the mineral eleonorite was discredited, and the ideal formula of beraunite was redefined from Fe2+Fe53+(PO4)4(OH)5 ⋅ 6H2O to Fe63+(PO4)4O(OH)4 ⋅ 6H2O. Beraunite from Hrbek Mine usually forms prismatic crystals flattened on {100}; elongated along b axis, striated on {100} || b, up to 0.2 × 0.5 × 3 mm, often in radial clusters up to 6 mm in size in association with black goethite, olive-green to dark green dufrénite and yellow to orange cacoxenite. Beraunite is hyacinth red, dark red, or red-brown and has a light orange-red streak; crystals are translucent, with a vitreous luster. The symmetry of the structure was found to be lower (Cc) than reported in the past (C2/c); this has been proven by the crystal structure refinement, Robs= 2.7 % for Cc and ∼ 8 % for C2/m. Refined unit-cell parameters obtained from powder X-ray diffraction data of the original material of Friedrich August Breithaupt are a= 20.653(2), b= 5.1433(6), c= 19.241(2) Å, β=93.560(9)∘, and V= 2039.9(2) Å3. Calculated density is 2.961 g cm−3. Beraunite is optically biaxial (+), α= 1.768(2), β= 1.781(3), γ>1.805, 2Vmeas= 69(4)∘, and 2Vcalc is not possible to calculate. Dispersion of optical axes is strong, r>v. The orientation is Y=b, X≈a, and Z≈c. Pleochroism is strong; Z (brown-red) ≫Y>X (both brownish yellow). The empirical formula of the original beraunite sample calculated on the basis of P = 4 apfu is (Fe5.763+Al0.15Zn0.01)5.92(PO4)4.00O0.99(OH)3.77 ⋅ 6H2O. The 57Fe Mössbauer spectrum of beraunite neotype (National Museum, Prague) from type locality implies that all iron atoms in beraunite structure are exclusively trivalent, located at the M site with different next-nearest-neighbor configurations. There is no spectral evidence for Fe2+ or iron in some impurities (e.g., limonite).
- Published
- 2022
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- View/download PDF
44. Spectroscopic redshift determination with Bayesian convolutional networks
- Author
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Podsztavek, O., Škoda, P., and Tvrdík, P.
- Published
- 2022
- Full Text
- View/download PDF
45. Inheritance of Convexity for the $\mathcal{P}_{\min}$-Restricted Game
- Author
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Skoda, Alexandre
- Subjects
Computer Science - Discrete Mathematics - Abstract
We consider restricted games on weighted graphs associated with minimum partitions. We replace in the classical definition of Myerson restricted game the connected components of any subgraph by the subcomponents corresponding to a minimum partition. This minimum partition $\mathcal{P}_{\min}$ is induced by the deletion of the minimum weight edges. We provide a characterization of the graphs satisfying inheritance of convexity from the underlying game to the restricted game associated with Pmin. Moreover, we prove that these graphs can be recognized in polynomial time.
- Published
- 2017
46. Time Series Cube Data Model
- Author
-
Nadvornik, Jiri, Skoda, Petr, Morris, Dave, and Tvrdik, Pavel
- Subjects
Computer Science - Databases ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
The purpose of this document is to create a data model and its serialization for expressing generic time series data. Already existing IVOA data models are reused as much as possible. The model is also made as generic as possible to be open to new extensions but at the same time closed for modifications. This enables maintaining interoperability throughout different versions of the data model. We define the necessary building blocks for metadata discovery, serialization of time series data and understanding it by clients. We present several categories of time series science cases with examples of implementation. We also take into account the most pressing topics for time series providers like tracking original images for every individual point of a light curve or time-derived axes like frequency for gravitational wave analysis. The main motivation for the creation of a new model is to provide a unified time series data publishing standard - not only for light curves but also more generic time series data, e.g., radial velocity curves, power spectra, hardness ratio, provenance linkage, etc. The flexibility is the most crucial part of our model - we are not dependent on any physical domain or frame models. While images or spectra are already stable and standardized products, the time series related domains are still not completely evolved and new ones will likely emerge in near future. That is why we need to keep models like Time Series Cube DM independent of any underlying physical models. In our opinion, this is the only correct and sustainable way for future development of IVOA standards., Comment: 30 pages, 17 figures
- Published
- 2017
47. Learning Style as a Factor Influencing the Effectiveness of the Inquiry-Based Science Education at Lower Secondary Schools
- Author
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Jirí Škoda, Pavel Doulík, Martin Bílek, and Ivana Šimonová
- Abstract
The IBSE has become a rather frequently applied strategy of directing learning activities in teaching science subjects. However, results of the IBSE effectiveness are not clear. A more detailed analysis is required which will reflect learners' individual characteristics. Therefore, the main aim of this research is to discover what the effectiveness of IBSE reflecting individual learning style is. The learning style categorization followed the Honey and Mumford's variation on the Kolb's system. The IBSE effectiveness was detected by the didactic test consisting of 15 PISA-style tasks. The research was conducted in the sample of 332 learners who were exposed to IBSE for five months. Their knowledge was tested before, immediately after and four months after the IBSE approach was applied in lessons. The collected data were processed by ANOVA and Tukey HSD test. The results show that the highest short-term results were reached with learners preferring concrete sensing; the highest long-term results were reached with those of active processing of information. This finding might be caused by better use of metacognition and acquiring such individual metacognitive strategies which learners apply at utilization of information. Further on, the IBSE should focus on mechanisms of fixing the acquired knowledge.
- Published
- 2016
48. Identification of Artifacts and Interesting Celestial Objects in LAMOST Spectral Survey
- Author
-
Škoda, Petr, Shakurova, Ksenia, Koza, Jakub, and Palička, Andrej
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
The LAMOST DR1 survey contains about two million of spectra labelled by its pipeline as stellar objects of common spectral classes. There is, however, a lot of spectra corrupted in some way by both instrumental and processing artifacts, which may mimic spectral properties of interesting celestial objects, namely emission lines of Be stars and quasars. We have tested several clustering methods as well as outliers analysis on a sample of one hundred thousand spectra using Spark scripts running on Hadoop cluster consisting of twenty-four sixteen-core nodes. This experiment was motivated by an attempt to find rare objects with interesting spectra as outliers most dissimilar from all common spectra. The result of this time-consuming procedure is a list of several hundred candidates where different artifacts are prominent, but also tens of very interesting emission-line spectra requiring further detailed examination. Many of them may be quasars or even blazars as well as yet unknown Be-stars. It deserves mentioning that most of the work benefitted considerably from technologies of Virtual Observatory., Comment: 4 pages, 2 figures. To appear in the proceedings of the Astronomical Data Analysis Software and Systems XXVI (ADASS XXVI)
- Published
- 2016
49. Identification of Interesting Objects in Large Spectral Surveys Using Highly Parallelized Machine Learning
- Author
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Škoda, Petr, Palička, Andrej, Koza, Jakub, and Shakurova, Ksenia
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
The current archives of LAMOST multi-object spectrograph contain millions of fully reduced spectra, from which the automatic pipelines have produced catalogues of many parameters of individual objects, including their approximate spectral classification. This is, however, mostly based on the global shape of the whole spectrum and on integral properties of spectra in given bandpasses, namely presence and equivalent width of prominent spectral lines, while for identification of some interesting object types (e.g. Be stars or quasars) the detailed shape of only a few lines is crucial. Here the machine learning is bringing a new methodology capable of improving the reliability of classification of such objects even in boundary cases. We present results of Spark-based semi-supervised machine learning of LAMOST spectra attempting to automatically identify the single and double-peak emission of H alpha line typical for Be and B[e] stars. The labelled sample was obtained from archive of 2m Perek telescope at Ond\v{r}ejov observatory. A simple physical model of spectrograph resolution was used in domain adaptation to LAMOST training domain. The resulting list of candidates contains dozens of Be stars (some are likely yet unknown), but also a bunch of interesting objects resembling spectra of quasars and even blazars, as well as many instrumental artefacts. The verification of a nature of interesting candidates benefited considerably from cross-matching and visualisation in the Virtual Observatory environment., Comment: 6 pages, 5 figures, Accepted for Proceedings of IAU Symposium 325 (Astroinformatics 2016)
- Published
- 2016
- Full Text
- View/download PDF
50. Hopf algebroids with balancing subalgebra
- Author
-
Škoda, Zoran and Stojić, Martina
- Subjects
Mathematics - Quantum Algebra ,Mathematical Physics ,16T10, 16T99 - Abstract
Recently, S. Meljanac proposed a construction of a class of examples of an algebraic structure with properties very close to the Hopf algebroids $H$ over a noncommutative base $A$ of other authors. His examples come along with a subalgebra $\mathcal{B}$ of $H\otimes H$, here called the balancing subalgebra, which contains the image of the coproduct and such that the intersection of $\mathcal{B}$ with the kernel of the projection $H\otimes H\to H\otimes_A H$ is a two-sided ideal in $\mathcal{B}$ which is moreover well behaved with respect to the antipode. We propose a set of abstract axioms covering this construction and make a detailed comparison to the Hopf algebroids of Lu. We prove that every scalar extension Hopf algebroid can be cast into this new set of axioms. We present an observation by G. B\"ohm that the Hopf algebroids constructed from weak Hopf algebras fit into our framework as well. At the end we discuss the change of balancing subalgebra under Drinfeld-Xu procedure of twisting of associative bialgebroids by invertible 2-cocycles., Comment: v3 accepted version; v2 old title A two sided ideal in Hopf algebroid axiomatics changed to Hopf algebroids with balancing subalgebra; thoroughly revised and extended from 18 to 29 pages, entirely new sections on weak Hopf algebras and on Drinfeld-Xu twists (the first submission to a journal planned within days, but suggestions still welcome)
- Published
- 2016
- Full Text
- View/download PDF
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